The United States said it will host a summit in Washington next month on preventing violent extremism, as European and American leaders call for stronger measures to monitor people online and at borders.

U.S. Attorney General Eric Holder announced the February 18 meeting from Paris on Sunday, where he joined an emergency conference on terrorism in the wake of a terror spree in France last week that killed 17 people.

"We must deal not only with holding accountable those people who would perpetrate such heinous acts. We must also deal with underlying causes that cause these things to occur, that somehow radicalize these people to take actions that we all find to be an affront to humanity," Holder said.

"We will bring together all of our allies to discuss ways in which we can counteract this violent extremism that exists around the world," he added.

In a statement, the White House said the meeting will highlight "best practices and emerging efforts" from several U.S. communities carrying out pilot programs to address extremism.

Lone wolf attacks

Speaking on CBS's Face the Nation program, Holder also said the “decimation” of core al-Qaida has reduced or eliminated that group's ability to carry out a 9/11-style attack, but he said affiliates like al-Qaida in the Arabian Peninsula have stepped in to try to inspire people to carry out smaller attacks.

“I think the possibility of such attacks exists in the United States,” he said.

“It is something that, frankly, keeps me up at night worrying about the lone wolf or a very small group of people who decide to get arms on their own and do what we saw in France this week,” Holder added.

However, Holder said Americans should feel secure with U.S. officials' efforts to prevent attacks by Islamist militants.

Interior and justice ministers from Europe and the U.S. gathered in Paris on Sunday, calling for increased Internet surveillance and stricter border security to counter attacks like the massacre at the Charlie Hebdo weekly newspaper. Journalists and police were reportedly targeted in the deadly shooting, raising questions about freedom of speech and of the press.

Sharing information

French Interior Minister Bernard Cazeneuve, who convened the ministerial meeting, said Europe must improve information sharing across borders and better track passengers traveling between countries.

"We are convinced of the necessity of this system at a European level to monitor those who go to theatres of war to fight as terrorists and come back, and to fight against organized terrorist networks," Cazeneuve said.

Cazeneuve said that "fundamental liberties" would be still respected under increased surveillance measures.